Issues with inclusion and interpretation : a cause for concern in mHealth reviews?

We read with interest the systematic review by Wang et al. (2018) on “the effectiveness of mobile apps for monitoring and management of mental health symptoms or disorders”; which sought to identify all studies of mobile apps for ‘mental health in all ages’, across a broad range of outcomes (including mood disorders, psychotic disorders, along with sleep, substance use and suicidal behaviours), including both single-arm studies and randomized controlled trials (RCTs). Given this very broad scope, we were surprised to see the authors included just 16 apps, only 5 from RCTs - particularly given that recent metaanalyses of smartphone interventions focused on single mental health outcomes, such as anxiety (Firth et al., 2017a) and depression (Firth et al., 2017b) identified 9 and 18 RCTs, respectively, for these outcomes alone.